Always on busy light led on wh66 base not extension

[supranet2022]

Dear community,

I just bought a Yealink WH66 with an inductive charging station, and several times for a customer. So the device is connected to different computers. Firmware 125.435.0.10 104.35.0.6.

What I don't understand or can't find a setting for is, that the red busy light LED on the base station itself, at the top right of the display, always lights up red. I can't find a setting on the computer or Yealink to turn it off, or the reason why it lights up red. It lit up red immediately after I unpacked and attached the headset. Yealink USB connect is installed and even if all soft clients are closed, it always lights up red.

Not bad but a bit annoying - is there a setting here that I'm missing??

Thank you